[1] Mary was born at Appleby Manor near Kittanning, Pennsylvania in Armstrong County on June 19, 1843.

[6][7] Together, they had five children that survived childhood: She died, a few days before her 87th birthday, on June 9, 1929, of pneumonia.

[6][7][18] After her husband's death in 1889, she used the wealth she inherited to fund archaeology research, including funds for prominent women archaeologists including Alice Fletcher and Zelia Nuttall.

[3] Thaw was also the primary philanthropist supporting the Omaha Presbyterian Theological Seminary.

After her initial contribution of the Cozzens Hotel in downtown Omaha in 1902, she made regular donations, practically underwriting the institution.